An orbiting spacecraft frequently relies on ground processing equipment to generate signals for correcting its orbital path and adjusting its altitude. These corrections are typically derived from theoretically predicted values, referred to as "predicts", and up-linked to the spacecraft's navigation and guidance system. Synthetic aperture imaging radars usually depend upon spacecraft altitude data to produce good image fidelity of targets. Many spacecraft do not have onboard altimeters, and imaging radars must derive their data from non-real time predicts. The predicts are then used in an informational feedback loop with the spacecraft's guidance system to produce spacecraft orbital corrections. For an earth tracking imaging radar, pointing corrections for the imaging radar antenna are affected by the spacecraft's attitude (i.e. pitch, yaw, altitude and earth's rotation). Whereas pitch, yaw and earth's rotation errors can be compensated by other means, altitude produced pointing errors can be compensated either by changing the spacecraft's altitude or by changing the pulse repetition frequency (PRF) of the imaging radar. In the later case, the radar parameters are changed by earth command to accommodate predicted variations in altitude. These predicted variations in altitude are frequently somewhat in error and thus affect the quality of the radar image obtained, i.e. produce ambiguities during data correlation. This problem is especially apparent with synthetic aperture radars where accurate altitude information is essential in order to successfully correlate the radar return signals. The present invention provides an echo tracking/ranging system which can be utilized in an orbiting spacecraft to rapidly provide accurate tracking and altitude information. However, the echo tracking/ranging system of the invention can be utilized in any system which transmits pulses and receives echo pulses from a target whose signature and/or range is to be determined. Thus, the invention can be utilized in conjunction with radar, pulsed laser or sonar systems.